The present invention relates to a dynamoelectric machine and particularly to the construction of a rotor having an integral cooling means.
Dynamoelectric machines are highly developed devices and which generally include a fixed stator supporting a suitable field winding and a rotor carrying an armature winding. A generator for producing an alternating and particularly three phase alternating current output may be of a rotating field construction in which a main salient pole field and small brushless exciter for providing DC current to the main field are mounted as the rotor within a stator having a polyphase output winding. In the salient pole system, the rotor includes a plurality of poles each of which carries a field winding which is series or parallel connected with the other field windings. A particularly satisfactory rotor structure is manufactured and sold by Marathon Electric of Wausau, Wisconsin, in which the rotor amortisseur winding and coil support is die cast as an integral part of the rotating field rotor. Thus, the four poles are formed from one piece laminations with appropriate amortisseur winding and clamping openings, and the end rings and amortisseur winding is integrally formed of a die cast aluminum resulting in high mechanical integrity and low vibration at operating speeds. The rotor pole assembly is then heat shrunk and keyed to the support shaft. The field windings are wound on the poles with suitable pole insulation.
In such generators and like dynamoelectric machines cooling is required to prevent overheating of the windings which must be maintained during operation within a maximum safe operating temperature. Generally, fan means are coupled to the shaft to establish an air flow through the generator and thus over the stator and rotor surfaces, particularly the main field winding structure. It is important that efficient cooling be created, with the air distributed more or less evenly over the field surface and with minimal recirculation of hot air. Although various cooling systems have been suggested, they have generally provided a flow-through pattern relying on a high volume movement over the component parts to establish the effective cooling of the winding.